Titania, titanium oxide (IV) or titanium dioxide is a chemical compound with a TiO2 formula. Among others, it is used in heterogeneous catalysis processes as a support and/or a catalyst.
Titanium oxide (IV) TiO2, is found in nature in various forms:                rutile (tetragonal structure),        anatase (tetragonal structure), and        brookite (orthorhombic structure).        
It has been formed into the following nanostructures:                nanotubes,        nanosheets,        nanofibers, and        nanowires.        
TiO2 has many advantages as semiconductor material, such as a wide interval of Energy bandgap (Eg), high oxidizing power, biological and chemically inert power and its non-toxicity.
The catalytic properties of TiO2 widely depend on its chemical and physical properties, and determine its texture and morphology characteristics and specially its dimension and crystalline phase. Specifically, the dimension in titania represents a huge factor in its catalytic properties, for example nanostructured titania or TiO2 nanocrystals are actually a reference point for its applications, being the major catalysis field.
Also, the properties inherent to nanostructured titania or nanometric crystal size are related to, if the crystal size is decreased, the increase of the surface area is achieved with its corresponding dimension, in the distribution of diameter and pore volume. Actually, the nanostructured materials, in its version as: nanocrystals, nanotubes, nanofibers, nanospheres, nanosheets, nanowires, are the new alternatives and opportunities for its application as materials that have a promising efficiency in a great variety of fields. These nanostructured materials have fundamental exceptional properties in its special physicochemical properties that give special catalytic, electronic, magnetic, mechanic and optic properties.
The titania nanotubes were discovered in 1990. The main applications were in photocatalysis and in solar cells to produce energy. In this investigation, it was found that titania nanotubes have a major surface area and interfacial transference speed of the load compared with TiO2 nanocrystals. For example, it was found that the positive transference of the load along the nanotubes could reduce the recombination of the hole-electron pair formation (Eg), allowing them to be highly efficient in photocatalytic decomposition and in photocells compared with TiO2 nanoparticles.
On the other hand, the titania synthesis with specific structure characteristics (particles, fibers, sheets, wires, tubes, etc.) and size (nano), and the formation mechanism, are the most important two points in the cutting-edge technology related to titania. Actually, TiO2 nanowires, nanotubes and nanofibers synthesis routes are contemplated through condensed electrochemistry and chemistry that are under investigation.
In the last decade, the methods used for titania nanotubes synthesis are: Chemical Vapor Deposition (CVD), anodic oxidation and humidity chemistry (sol-gel and hydrothermal methods). In all of them, the objective is to obtain special nanotubes arrangements with better characteristics of surface area and pore volume and with specific structure arrangements. Among the more recent methods of condensed chemistry for preparing titania nanotubes are the following: via surfactants, synthesis via alumina as a quencher, irradiation via microwaves, electrochemical synthesis and new routes of hydrothermal method.
Each above-mentioned method has advantages and disadvantages in the final characteristics of the obtained titania nanotubes, for example, in the synthesis via alumina as a quencher, it is possible to obtain uniform and well aligned nanotubes. Nevertheless, they have a larger size due to alumina porosity that serves as a cast, obtaining pore diameters of up to 50 nm. Generally the walls are constituted of TiO2 nanoparticles, so that when trying to separate them, sometimes part of them are destroyed. Therefore this method is not practical.
Regarding the method via surfactants, it is possible to obtain titania nanotubes with very small pore diameter and very thin walls. Compared with all other methods, its limitations are based on processes with long and complicated preparation, which greatly increases its cost. The titania nanotubes with a 10 nm size are made through the hydrothermal method starting from titania nanocrystals, but using high sodium hydroxide concentration, where the alkali ions are interchanged by protons to form H-titanates. Different phases are obtained through this method, such as anatase, rutile and brookite that are dependent of the synthesis temperature. In this method, the mechanisms and control of the formation ratio of the above-cited crystalline phases that seem to show high dependence of the thermal treatments are still being investigated.
In preliminary studies on formation of titania nanotubes starting with titania nanocrystals through hydrothermal methods nanotubes with diameters of 8-10 nm were obtained, with lengths of 50-200 nm and specific areas of 380 to 400 m2/g, where the bonds Ti—O—Ti, change to Ti—O—Na. In this condition, the anatase phase exists in a metastable condition as a “soft chemical reaction” at low temperature. As the following step in this method, washings with HCl are carried out, for the ionic interchange of Na for H and forms again Ti—O—Ti, continuing washing with deionized water to form Ti—OH or Ti—O°°°°H—O—Ti species, these materials have very specific applications, as in photocatalysis.
Some investigators take the position that the hydrothermal treatment is the fundamental step for obtaining titania nanotubes with special texture and morphology characteristics, leaving washing on the second place. Nevertheless, other investigators establish the contrary, that is, the washing is a fundamental step for obtaining nanotubes. Other groups comment that in each case the nanotubes are obtained for different applications. Among the main existing debates of using one or another synthesis method, is what type of crystalline structure forms of nanotubes can be obtained, as can be i) anatase/rutile/brookite TiO2, ii) lepidocrocite HxTi2.x[ ]x4O4 (x-0.7, [ ]: vacancies), iii) H2Ti3O7/Na2Ti3O7/NaxH2-xTi3O7, iv) H2Ti4O9. Also, it is established that starting with the anatase phase, nanotubes are easily formed compared with those when the nanotubes start from rutile. Another very important factor is the size of the crystal of the starting material.
According to the present invention, it is concluded that starting from titania powder in the anatase phase, the nanotubes are more easily obtained with better arrangement and structure size as compared with starting with the rutile phase. Furthermore, when these nanotubes are hydrated, they convert into hydrated hydrogen titanates (H2Ti3O7.nH2O(n<3)), and have special morphology such as: multi-walls and order spacing of 0.75-0.78 nm.
The studies propose that obtaining tri-titanates nanotubes through hydrotreatment are made by two mechanisms: i) starting with the titanium dioxide and a concentration solution of sodium hydroxide (NaOH), obtaining Na2Ti3O7 as an intermediate product, converting them into tri-titanates in form of nanosheets (Ti3O7)2−), where this formation depends of the NaOH concentration to be finally converted into titania nanotubes. Nevertheless, not all H2Ti3O7 are converted in titania nanotubes. ii) starting with sodium lepidocrocite Na2Ti3O7, that tend to form titania nanocrystals, but are not stable and also influences the Na+ ion concentration to form nanocrystals and to finally form titania nanotubes. It is said that the expansion of titania particles originates the formation of Na2Ti2O4 (OH)2, where depending on the concentration of NaOH solution, the short Ti—O bonds slide and expand to form linear bonds (one-dimensional), O−—Na+—O−, to produce bidimensional flat fragments, whereas nanotubes already, would eventually establish covalent bonds.
On the other hand, an important factor in the application of hydrothermal treatment, is related to the temperature, where it is established that when titania is reacted at a high temperature (250° C.) in presence of a NaOH solution, Na2Ti2O5°H2O is formed. In order to remove Na+ ions, it is washed with HCl and the formation of sheets, in this case nanosheets, is started.
Specifically, the main factors that influence the formation of titania nanotubes with special physicochemical characteristics are those described below, in the order of sequence of the hydrothermal method:
Synthesis precursors                Rutile        Anatase        Degussa P25 nanoparticles        TiIV Alkoxide        SiO2—TiO2 mixtures        
In the synthesis of titania nanotubes through hydrothermal method, the starting reagents have a very important role, for example, starting from normal powder of an anatase/rutile mixture or anatase/rutile nanocrystals; or titanates sheets (Na2Ti3O7); or titanium salts (TiCl4); or titania alkoxide (Tiiv); or TiO2 doped anatase; or SiO2—TiO2 mixtures. Generally, the titania nanotubes with external diameter of 10 to 20 nm can be obtained starting with titania powders with big particle size, such as: TiO2-rutile, TiO2 Degussa (P25) or SiO2—TiO2 mixtures. Also, taking the crystal size of the starting material as a reference, starting from TiO2 rutile with average particle size of 120 to 200 nm and high concentration of NaOH (10N) at 150° C. for 48 hours, multilayer and “open-ended” nanotubes are obtained, with an internal diameter and length of 2-3 nm and 50-200 nm, respectively, furthermore, with an uniform winding. Similarly, commercial titania was used such as: TiO2 Hombikat UV100 and TiO2 BCC100, with which the nanotubes with internal and external diameter of 3-6 and 7-10 nm, respectively, were obtained and with a length of about 400 nm.
In recent studies, other types of materials were used, such as: i) fresh gels, ii) P25 Powders, iii) TiO2 treated at 500° C. and all of them were treated with hydrothermal method. Nanotubes with lengths from 50 to 70 nm and with average diameter of 10 nm were obtained using fresh gels. The nanotubes made of P25 showed average diameters of 50-300 nm and nanotubes with various hundreds of nanometers and with an average diameter of 15 nm were made with TiO2.
Hydrothermal Method                NaOH Normality/Starting material (TiO2) relation        Operation conditions (time, stirring)        Synthesis temperature        
The temperature has a very important role in the hydrothermal method, for example, it is possible to form titania nanotubes in an interval of 100 to 180° C., starting with TiO2 powder, that can be a mixture of anatase/rutile phases with a performance of 80 to 90% and if it is out of the above-mentioned interval, the formation of nanotubes decays. Also, there is a combination of a temperature interval with NaOH concentration and the particle size of the starting titania, for example, at a temperature from 100 to 200° C. and NaOH 10N, starting with TiO2 nanoparticles, the specific area, diameter and pore volume of the obtained nanotubes are increased.
Another combination of variables of the hydrothermal method is the combination of temperature and aging time, for example when the aging time is of 72 hours at 150° C., a greater performance in the obtention of nanotubes with a defined crystallinity grade (titanates) is obtained.
Based on the above, most investigations define that with a hydrothermal method at a temperature less than 100° C., the nanotubes are not formed, only nanosheets can be obtained through this method; also, it is said that the determining step to obtain nanotubes is starting with sodium titanates that appear at 70° C., as nanosheets, which, incrementing the temperature at 90° C., convert into nanofibers.
Through the hydrothermal method at a temperature of 160°, the specific area and the pore volume in nanotubes decreases due to the interlayer spaces limitation and due to the fact that the sodium ions are not replaced by the hydrogen in the washing process with hydrochloric acid. As well, at a temperature of 170° C., the nanobars occur also with decrease in the area and in the pore volume.
Pretreatment-sonication                Nanoparticles dispersion        Inhibition of crystal growth        Particles homogeneity        Influence in length distribution        Synergy in reactions        
The sonication treatment in nanostructures is commonly used in nanotechnology to disperse nanoparticles, especially in liquid media. Referring to titania nanotubes, the length is controlled by means of the hydrothermal method. The sonication speed depends on the nanoparticles dispersion for the intermolecular reaction among the TiO2 particles and NaOH solution, besides of rendering the system more homogeneous.
The migration of OH− and Na+ ions can be carried out through the sonication treatment all along the holes restricted between the particles of the used titania precursor that will help not to delay the nanotubes formation. Other property attributed to the sonication treatment is that the obtained nanotubes with an average length of 3 to 9-fold the nanotubes without treatment also increases its specific area.
On the other hand, the irradiation to a different magnitude as the interval of 100 W to 280 W and up to 380 W impacts the morphology of the nanotubes, for example, small diameters (1 to 14 nm) are obtained with magnitude from 100 and 280 W and with high magnitude (380 W) it increases substantially, from 199 to 600 nm. Also, the sonication during the preparation of nanotubes helps to avoid the growth of TiO2 crystals. Definitely, the sonication treatment helps to obtain nanotubes with greater length, with small diameters and high specific area.
Thermal Treatments                Effect on the structure of the phases        Titanate nanotubes microstructures        Transformation of phases        Titanate nanotubes in anatase phase        
The thermal post-treatments after applying the hydrothermal method have an important effect in the final morphology of the nanotubes. It is possible to modify the nanostructures obtained with hydrotreatment with calcination treatments, for example, it is possible to transform the titanates again into TiO2 anatase phase, with heat; therefore, nanotubes were stabilized up to a temperature of 500° C. with 8 to 22 nm diameters, starting with pure anatase. It is important to point out that the temperature has an important role in the crystallinity grade of the titania nanotubes, for example TiO2 powders calcinated at 400° C., give nanotubes with thin walls but its structure is equal to the structure not submitted to this calcination temperature, nevertheless in a range of 600 to 800° C., the nanotubes structure collapsed. Based on the above, the effect obtained increasing the calcination temperature over the crystallinity and nanotubes structures, is permanent, for example, the crystal size is increased from 5 to 30 nm, the average pore size is from 18 to 33 nm, the pore volume is of 0.99 to 0.35 cm3/g and the specific area is of 220 to 64 m2/g with a temperature increase of 300 to 600° C.
Generally after the washing process and a calcination temperature greater than 500° C., the structure of the nanotubes is lost, converting it into TiO2 nanoparticles but with a greater size of the crystal that those obtained when are submitted to hydrothermal treatment to transform them into nanotubes; also in nanocrystals submitted at a temperature greater than 600° C., the anatase phase is diminishing and losing to be converted into rutile.
Washing Process                Determines elemental composition        Alignment of the nanotubes specific area        
A great part of the carried out studies determine that the morphology and dimensions of the nanotubes are determined by the hydrothermal method more than by the washing processes; nevertheless, other studies attributes an important influence, such as the nanostructures or initial phase of the nanotubes, its specific area and greater purity. Based on the above, the interchange of Na+ ions by H+ ions in the washing process increases spaces and furthermore increases the area.
The effect of concentration of HCl is also analyzed. It is said that an interval of optimum concentration is of 0.5 to 1.5 M, where below 0.5M, the withdrawal of Na+ is inefficient and above 1.5M the nanotubes can be destroyed, forming “lumps” with a size greater than 100 nm; nevertheless, in a study carried out with HCl 0.1M at 150° C., the nanotubes were obtained with great efficiency and also the length was decreased. Also, other studied argue that when the Na+ ions are withdrawn, the nanotubes are destroyed or the pore volume substantially diminishes, as well as its specific area. When low concentrations of NaOH are used (0.01M to 0.001M), the length of “open-ended” and multilayer nanotubes was of hundreds of nm with an average diameter of 10 to 30 nm. The combination of TiO2 starting materials and HCl concentration shows an effect, for example, starting with TiO2 rutile and 0.1M of HCl, firstly, the nanotapes are obtained, but not all these nanostructures are converted in nanotubes, therefore, the washing at a greater concentration of HCl is essential if it is desired to increase the nanotubes formation.
The XRD technique can be applied in qualitative analysis as well as in quantitative analysis of the TiO2 nanostructures, where by means of these techniques, it is possible to identify the types of nanostructures of which are constituted, its ratio and to determine its dimensions. The previous information can be obtained through the application of fundamental tools, such as: Bragg's law and the Formula for Integrated Intensity. The information that can be obtained is as follows:                Space group and geometry of the elemental cell obtained from the collection of Bragg's angles (2θ); as well as with these values, the qualitative identification of the crystalline phases can be carried out;        Determination of the crystal size through the peak broadening method. The crystalline purity can also be determined is with this method.        Atomic position in the elemental cell, through the measuring of the Integrated Intensity of the peaks, which also allows to carry out the quantitative analysis of the phases present in the sample; and        Texture analysis, residual tensions and phases diagram measuring.        
On the other hand, by means of Fourier transform infrared spectroscopy (FTIR), it is possible to identify the operational groups in TiO2 nanostructures, such is the case of identification of OH groups, which determines the hydroxylation grade, important characteristic of titania as catalytic material. The acid surface of the supports and catalysts can also be determined and there are various forms for this determination, such as: NH3 adsorption on the catalyst surface and pyridine adsorption.
Pyridine as widely used as a probe molecule for the identification of both Lewis and Brönsted sites; the pyridine molecule can interact through the ion pair containing the nitrogen (N) with different sites. Generally, the band associated to 1640 and 1540−1 are associated to Brönsted, meanwhile the 1630 and 1440, 1445 cm−1 region is attributed to the coordination of Lewis sites, the band to 1490 is associated to both Lewis and Brönsted sites.
The main bands associated in the interval 1850-1680 cm−1 are related to NH4 chemisorbed vibrations in Brönsted sites, the bands located at 1600 cm−1 and 1217 cm−1 are related to the vibrations of coordinated N—H bonds in Lewis acid sites. Even these two techniques can help us to determine the type of the sites present in the spectra catalyst via ammonium, it is not clear, because they can be placed on the top with other different types of bands that can cause problems for quantifying the real acid sites, contrary to the analysis with pyridine, since this technique is very assertive and allows cleaning the area where there are pyridine adsorbed sites to be able to clearly quantify the sites present in the supports and catalysts.
The determination of bandgap energy or bandgap (Eg) of TiO2 is fundamental to know the activity in the catalytic process and are obtained from the UV-vis spectra en 200-800 nm region. There is fundamental transition in this region, from the valence band to the conduction band, in this case for nanostructures of nanotubes or H-titanates type.
Also, it is important to point out that it is possible to determine the morphology (phases) and the dimensions of TiO2 nanostructures by means of the Transmission Electron Microscopy (TEM) analysis and also, it is possible to obtain the individual diffraction pattern through the selection of a crystal in different micrograph areas, besides of its interplanar corresponding distances with Digital Micrographs program that are compared with classified cards of JCPDS for TiO2 (JCPDS—Joint Committee on Powder Diffraction Standards), determining the structure of the crystal in its corresponding direction (hkl).
On the other hand, the physical and chemical properties of a material are determined by the type of interaction existing among the electrons and among ions and electrons; when reducing the space where the electron can move freely, it is possible that new effects will occur due to the space confinement, what causes the modification of the energetic levels of the electrons within the particles. Based on the above and to the fact that surface to volume ratio is notably increased, the nanotubes have new properties that do not occur nor in great quantity in the material (“bulk”), neither in the fundamental entities constituting the solid.
There are two types of nanotechnology for preparing nanostructured materials:                The “Top-Down” method refers to design of nanomaterials with size reduction (from largest to smallest size) and is based on the mechanisms for obtaining structures in a nanometric scale. This type of nanotechnology has been used in different fields, being the field of electronics the one with greater application; nevertheless, other fields were recently incorporated, such as medicine and environment protection; and        The “bottom-up” method that refers to auto assembly, literally from a smallest size to a biggest size and starts with a nanometric structure such as a molecule and by means of a mounting or auto assembly, a greater mechanism than the starting mechanism is created. This focus is considered as the only “real” nanotechnology focus that allows to extremely and accurately controlling the nanometric size of the material.        
Some of its properties are:                Increase of the surface area/volume inducing a great increase in the interfacial area of the species on the surface;        Changes in the electronic structure of the species conforming the nanostructure;        Changes in the arrangement (crystalline structure, walls and distances and internal and external diameters, etc.) of the species in the nanotube and presence of defects; and        Confinement and quantum-size-effect due to the confinement of the charge carriers within the nanotube.        
Among the main patent documents of the state of the art identified as the closest to the present invention are the following:
WO 2006/019288 for “Selective Absorption Material and Application Method Thereof”, dated Feb. 23, 2006, José Antonio Toledo and Maria Antonia Cortés Jacome, relates to a method for the selective absorption of nitrogen- and sulfur-bearing compounds contained in different fractions of petroleum hydrocarbons. The solid material used as an absorbent consists of a nano-structured material comprising morphology of nanofibers and/or nanotubes of an inorganic oxide of a metal from group IVB with a high specific surface area of between 100 and 600 m2/g and is not promoted with a transition metal. The material, object of the present invention, also can be used as adsorbents of other contaminants and various materials, characterized because it comprises the following steps:
1. Selective adsorption of nitrogen and/or sulfur compounds of light and intermediate petroleum fractions contacting said charges with a nanostructured TiO2-x material.
2. Nanostructured TiO2-x material with nanotubular morphology, high deficiency of oxygen, beta phase crystalline arrangements and/or JT orthorhombic and/or anatase structure, with or without transition metals.
3. Method for preparation of nanostructured TiO2-x with transition metals. Characterized by a hydrogen titanate and/or mixed titanate from hydrogen and sodium, submitted to an ionic interchange with Cu and Zn oxides.
4. An adsorbent material, such as nanostructured TiO2-x, with specific area values from 50 to 500 m2/g and a pore size of 2 and 10 nm.
5. An adsorbent material, such as nanostructured TiO2-x with a orthorhombic structure whose unit cell is described by the space group Pmmn 59, has a peak X-ray diffraction about 10 degrees in a 2Θ scale in the plane (200) and a number of structural layers of 1 to 50.
6. An adsorbent material such as nanostructured TiO2-x characterized having a composition comprised between 0 and 20% by weight of Zn, Cu, Ni, Co, Fe, Ag, Mn, Cr, Mo or W, preferably Cu or Zn.
Where;                TiO2 anatase phase and/or TiO2 rutile phase and/or amorphous titanium hydroxide and/or directly a mineral called rutile are used as starting materials;        Hydrothermal treatment of the previous aqueous solution with stirring between 100 and 250 rpm and at a temperature from 50 and 300° C., to a autogenous pressure in the range of 1 to 50 atm;        Ionic interchange treatment with diluted acid solution from 0.1 to 1M, using organic and inorganic acids, such as: hydrochloric, sulfuric, nitric, hydrofluoric, boric and phosphoric acid or ammonium salts capable of interchanging sodium in a pH range of 1 to 7;        The nanostructured TiO2-x material, classified according to the crystallographic structure determined by X-ray diffraction, such as rutile type TiO2, or anatase and/or mixes of both of them and/or amorphous titania, by its physicochemical properties can be used for the application in the selective adsorption of nitrogen and/or sulfur compounds of petroleum light and intermediate fractions.        
WO 2007/141590 for “Sol-gel nanostructured titania reservoirs for use in the controlled release of drugs in the central nervous system and method of synthesis”, published on Dec. 13, 2007, Lopéz-Goerne T. refers to a sol-gel nanostructures TiO2 which is biocompatible with brain tissue. In the nanostructured TiO2 of this invention, the pore size distribution, crystallite size and the extent of the crystalline phase distribution of anatase, brookite and rutile can be fully controlled. These materials can be used to contain neurological drugs and can be inserted directly into brain tissue for the purpose of the controlled time release of drugs over a period of from 6 months to three years.
WO 2007/027079 for “Method of preparing a catalytic composition for the hydroprocessing of petroleum fractions”, published on Mar. 8, 2007, Toledo J., relates to a method of preparing a catalytic composition comprising at least one non-noble metal from group VIII and at least one metal from group VIB of the periodic table. The catalytic composition has a high specific activity in reactions involving the hydroprocessing of light and intermediate fractions, preferably in reaction involving the hydrotreatment of hydrocarbon steams, including hydrodesulphurization (HDS), hydrodenitrogenation (HDN) and hydro-dearomatisation (HDA).
WO 2007/027079 for “Palladium and nickel modified Mo/Alumina-titania sulfide catalysts on the hydrodesulfurization of 4,6-dimethylbenzothiophene”, published on May 15, 2012, Vargas E., relates to the addition of Pd (0.3-0.8% by weight) and Ni (NiO=3.1% by weight), to Mo (MoO3=10.0% by weight) over sulfide alumina-titania (MO/AT) catalysts. The addition of Pd and Ni over MO/AT catalysts has a positive effect producing a sulfide catalyst, approximately 8 fold more active for HDS of the 4,6-DMDBT molecule, favoring the hydrogenation (HYD), promoting the removal of S through hydrogenated partially 4.6-TH-DMDBT compound, producing 3,3-DM-CHB. Furthermore, with an effect between Pd and Ni over the MO/AT catalyst that is greater when the Pd is incorporated in the Ni-MO/AT catalyst, than when the Pd is incorporated into the Mo/AT catalyst.
On the other hand, WO 2005/105674 for “Nanostructured titanium oxide material and method of obtaining same”, published Nov. 10, 2005, Toledo A., relates to nanostructured materials comprising titanium oxide (TiO2-x, wherein 0=x=1), having an orthorhombic unknown crystalline structure which is the basic unit in the construction of nanofibers, nanowires, nanorods and/or nanotubes, which are produced from an isostructural precursor comprising hydrogen titanate and/or mixed sodium and hydrogen titanate, corresponding to the hydrogenated, protonated, hydrated and/or alkaline phases of the aforementioned structure, and are obtained from titanium compounds, such as: titanium oxide having a crystalline anatase structure, amorphous titanium oxide, titanium oxide having a crystalline rutile structure and/or directly from rutile mineral and/or ilmenite. The invention also relates to the method of obtaining the inventive materials.
U.S. Pat. No. 1,156,210 for “Process for manufacturing a catalyst or catalysts based on titanium oxide and its application in sulfur synthesis Claus process”, published on Nov. 1, 1983, to Dupin refers to a improved process for the obtention of catalysts or catalysts support based on titanium oxide for sulfur synthesis Claus process, characterized because it comprises the following steps:
1) the kneading of a mix containing 1 to 40% by weight of water, up to 15% of conformation additive, from 45 to 99% by weight of a poorly crystallized and/or amorphous titanium oxide in powder showing a fire loss comprised between 1 to 50% by weight, is carried out;
2) the conformation of the mix is carried out; and
3) the mix is dried and afterwards, the products obtained at a temperature of 200 to 900° C. are calcinated.
U.S. Pat. No. 6,034,203 for “Catalysis with titanium oxide”, dated Mar. 7, 2000, to Lusting et al. relates to a process, which can be used in oligomerization, polymerization or depolymerization such as, for example, the production of polyester. The process comprises contacting a carbonyl compound, in the presence of a composition, with an alcohol. The catalyst comprises a catalyst having the formula of Mx Ti(III)Ti(IV)yO(x+3+4y)/2, wherein M is an alkali metal, Ti(III) is titanium in the +3 oxidation state, Ti(IV) is titanium in the +4 oxidation state, x and y are numbers greater than or equal to zero wherein if x equals to zero, y is a number less than ½.